RU2635596C2 - Method for manufacturing hollow metal workpiece by casting - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes placing a destructible rod (20) which comprises a base (22) made of a filler, a shell (40) attached thereto, and a frame 36 extending through the base and connected to the shell, inside the mould (50). The metal is melted, which under the pressure is pumped into the mould (50) surrounding the rod (20) forming the internal space of the part. After the part has cured, the base is ground and removed through the openings provided in the shell and in the part, the shell is destroyed and removed through the holes provided in the part.

EFFECT: high mechanical strength of shell.

10 cl, 5 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a method for manufacturing a hollow metal part by casting and, in particular, injection molding.

This method is particularly suitable for the manufacture of parts that have a hollow inner side and which, accordingly, cannot be directly removed from the mold, for example, liquid pipes or semi-closed containers (for example, housings).

State of the art

Casting refers to the processes of forming metals (i.e., pure metals or alloys), which consist of pouring liquid metal into a mold to form a specified part after cooling, limiting to a certain extent the possible finishing of the above part.

According to injection molding technology, a liquid metal is injected into a mold under a significant injection pressure, typically 100-1200 bar (i.e. 10-120 MPa). The injection rate into the mold is typically 10-80 m / s and the temperature of the molten metal is typically 400-980 ° C.

In foundry, injection molding is often used in mass production for the delivery of automobiles and home appliances to the market due to the high cost of tooling (molds and cutting tools).

Currently, for injection molding a hollow part, such as a pipe or a half-closed vessel, the caster casts two halves of the part, which are later mechanically assembled by welding or gluing. This solution is not satisfactory because, on the one hand, two sets of foundry equipment are required (one for each half of the part) and, on the other hand, the assembly phase is critical because of the need to ensure tightness in the assembly area.

Thus, there is a need for another manufacturing method.

Disclosure of invention

The present invention relates to a method for manufacturing a hollow metal part by casting, in which:

- provide for the destructible core, which includes a base made of filler, and a shell that surrounds the above base and is attached to it;

- the core is placed inside the mold;

- the metal is melted and the liquid metal is injected into the mold surrounding the core, while the core forms the inner space of the part;

- after curing the part, the core core is crushed and removed through the outlets provided in the shell and in the part; and

- destroy the above shell and remove it through the releases provided in the part.

The core used here is different from conventional cores used in non-pressure casting in that it has a shell that allows it to withstand the mechanical stresses exerted by the molten metal during injection. Without this shell, the core could be crushed by the above efforts. The shell is attached to the core base to prevent separation of the shell and base during injection, and since the shell is supported by the core, the latter takes up some of the force during injection.

This manufacturing method is particularly suitable for injection molding, since the forces exerted by the molten metal during injection are high, and the shell of the core fully confirms the advantage of its use. In this case, the mechanical strength of the shell is sufficient to withstand the injection of molten metal under pressure, and during casting, the molten metal is injected under pressure into the mold surrounding the core.

However, this manufacturing method can be used for casting in other applications, for example, in low pressure casting or non-pressure casting (for example, for casting iron-based alloys or non-ferrous alloys in metallic or non-metallic forms).

The choice of material forming the shell is based on the satisfactory mechanical strength of this material and its proper adhesion to the core. Some examples of materials are provided below, but those skilled in the art may, based on the present description, take into account the use of other materials.

Preferably, the shell-forming material also has one or more of the following properties:

- is chemically passive with respect to the injected metal and, in particular, does not dissolve in it;

- is impervious to metal injected under pressure;

- has a proper surface condition and, in particular, low porosity or no porosity. This allows you to more easily separate the shell from the molded part and ensure the proper condition of the walls of the inner space of the part.

The core shell is made, for example, on the basis of particles connected by a binder or binders of organic (e.g. polyurethane), mineral (e.g. silicate, colloidal silica, ethyl silicate, low melting point metals) or hydraulic (e.g. gypsum, cement, lime) origin . These particles may be clay-fired ceramics and may or may not contain zircon. They can be obtained by recycling the old shell. In another example, the shell is metal.

The core base, for example, is made of foundry sand or cast gypsum, possibly with a fibrous filler. The binder used to aggregate the core materials may be hydraulic, organic (e.g. cellulose) or inorganic (e.g. silicate). Fibrous fillers are of organic or mineral origin (e.g. flax, wood, glass).

To grind the base and remove the cast part, use the usual core removal process or a mechanical method (for example, shock, vibration, pellet or ultrasonic) and / or a hydraulic method (water jet) or even a chemical core removal method (for example, by dissolving a binder (binders) )).

In certain embodiments, the destructible core further includes a framework that extends through the core core and connects to the shell. This frame can be destroyed and removed simultaneously with the base and / or shell. Such a frame further enhances the mechanical strength of the core.

In certain embodiments, for manufacturing a core, the core of the core is performed by aggregating the material in a mold box having pins extending through the inside of the mold box, so that the base removed from the mold box has holes in which the pins are located and these holes are filled with material which forms the framework, for example, by immersing the core core in a solution of liquid clay, injecting (under low pressure) the same solution of liquid clay or pouring a solution of liquid clay by gravity into a container.

Holes and corresponding carcass elements (i.e. carcass elements formed by filling holes in the material forming the carcass) can pass completely or only partially through the core core.

In certain embodiments, the substrate is immersed one or more times in one or more baths with a solution of liquid clay to coat the substrate with one or more layers of a curable material. For example, gypsum can be used as a liquid clay solution. For example, the core core can be immersed in a first bath with a solution of liquid clay to form a framework, if any, and a lower layer of the shell, and then in other baths with a liquid solution of clay to form the upper layer (top layers) of the shell. Thus, the core base can be immersed in a first bath with a solution of liquid clay to form a skeleton and a lower layer of the shell, and then in one or more other baths with a liquid solution of clay to form the upper layers of the shell. Instead of dipping, the shell can be made by injecting a liquid clay solution.

The materials forming the shell and the frame may be identical or may differ from each other. In addition, the criteria that can be used with respect to shell and carcass materials need not necessarily correspond to each other. In particular, since the frame does not come into contact with the injected metal, its chemical passivity with respect to this metal is not a selection criterion. In addition, since the frame is subjected to lower forces during injection compared to the shell, the mechanical strength of the frame may be less high compared to the mechanical strength of the shell. In addition, in certain embodiments, it is desirable to remove the frame simultaneously with the base. In this case, the frame, like a base, is made of aggregated material that can be ground. Thus, there is the possibility of grinding and removing the base and frame in one operation during the core removal process.

In certain embodiments, for the manufacture of a core:

- the core is made by aggregating the material in a molding box provided with support elements passing (in whole or in part) through the inside of the molding drawer, and

- the shell surrounding the core, and the support elements are made so that the support elements pass through the shell.

The support elements are then used to hold the core in place during injection. Depending on the position of the support elements in the core, they can also serve to increase the mechanical strength of the core.

In certain embodiments, the support elements are hollow and form channels for the release of gases, which are formed during thermal decomposition of certain core components during casting. This allows you to limit the risks of deformation due to the effects of these gases, in particular when the part has thin walls.

In certain embodiments, the support members of the part are removed to provide channels through which the core and / or sheath are removed.

Other distinguishing features and advantages of the proposed method will become clear after studying the following detailed description. This detailed description is given with reference to the attached drawings.

Brief Description of the Drawings

The attached drawings are schematic and not drawn to scale; they are primarily aimed at explaining the principles of the invention.

In these drawings, identical elements (or parts of elements) are denoted by the same reference numbers.

FIG. 1 - molding box for the manufacture of the core core;

FIG. 2 is a side view of a core base made using the mold box of FIG. one;

FIG. 3 is a perspective view of a core made with the base of FIG. 2;

FIG. 4 is a sectional view of the mold in which the core of FIG. 3;

FIG. 5 is a perspective view of a hollow metal part obtained by molding in the mold of FIG. four.

The implementation of the invention

The following is a detailed description of an example method with reference to the attached drawings. This example illustrates the features and advantages of the invention. However, it should be noted that the invention is not limited to this example.

In FIG. 1, a molding box 10 is shown for manufacturing a core 22 of a core 20. This molding drawer includes halves 10A, 10B which, when assembled, form an open space 12 between them for accommodating materials that form the core of the core.

Inside the mold box, i.e. In the open space 12, the pins 16 continue. In this example, these pins 16 pass through the entire open space 12, and each pin 16 consists of two half-pins 16A, 16B, respectively, installed in halves 10A, 10B and arranged so that after assembly of the halves each of them is a continuation of another pin.

Supporting elements 18 are also located inside the molding box, which partially pass through the free space 12. In this example, these elements 18 are hollow and have a tubular shape with a conical (in the form of a truncated cone) free end 18E. The other end of these elements 18 rests on one of the walls 15. Each element 18 has an internal channel (hole) passing through it, open at both ends of the element.

To make the core base 22, the open space is filled with a filler, for example, sand particles mixed with at least one curable resin. After the curing of the resin (s) (for example, by heating or using catalyst gas), the sand particles aggregate and form the base 22. Then the base 22 is removed from the mold 10.

As shown in FIG. 2, the base 22 has holes 26 instead of the pins 16. In addition, the support elements 18 are recessed into the mass of the base 22.

For the manufacture of the core 20, the base 22 is immersed one or more times in one or more baths with a liquid paste or liquid clay, so that the base is covered with one or more layers of curable material. To hold the base 22 during immersion, hollow support elements 18 are used. Pins are installed inside the elements 18, which allow holding the base 22 and close the inner channel of the elements 18 to prevent them from filling. After each immersion, the deposited layer cures, for example, in air.

During the first immersion in the first liquid clay bath, the openings 26 of the base 22 are filled and form the frame 36. Thus, the frame 36 consists of several elements that pass through the core 22 and are connected to the shell 40. In this example, the frame elements are similar to the openings 26 pass along the entire base, so both ends of each frame element are connected to the shell 40.

The first liquid clay solution also forms the first layer or lower layer of the shell 40. Other layers, if provided, of the shell 40 can be formed by immersing the base 22 in other baths with curable materials.

In order to cover the substrate 22 and fill the holes 26, instead of immersion operations (or in addition to the immersion operations), injection or gravity pouring of a clay liquid solution around the substrate and / or into the substrate may be provided.

In FIG. 3 shows the core 20 obtained after molding the sheath 40 surrounding the base 22.

As an example, it is possible to manufacture the core 20 from the following materials and under the following conditions: for the manufacture of the base 22, molding sand pre-coated with resin and a hardener is used, and the resin solidifies through the use of a hardener. For example, the sand used is AFS 55 grade silica. The grain size of the sand may vary depending on the shape and size of the core used. The resulting base 22 is then immersed in a refractory liquid clay solution mixed with colloidal silica. During the first dive, the openings 26 are filled with a liquid clay solution to form a framework. The base 22 is dried and then again immersed in a solution of liquid clay the required number of times to obtain the desired thickness of the shell 40 after final drying.

After the manufacture of the core 20, it is placed in the cavity 51 of the mold 50, as shown in FIG. 4. This figure shows a sectional view of a mold 50 and a core 20. The core 20 is held in place in the mold 50 by means of hollow pins 53 attached to a portion of the mold 50 and inserted into the supporting elements 18 of the core 20.

The metal is then melted and molten metal is injected into a mold surrounding the core 20. The metal can be injected under pressure, while the sheath 40 withstands the forces exerted during injection and maintains the integrity of the core 20. In addition, the gases generated during thermal decomposition of certain elements (usually binders) that make up the core 20, mainly outward form 50 through the internal channels of the supporting elements 18 and pins 53. This release of gas gases Referring to FIG. 4 arrows G.

After curing and cooling (full or partial) of the metal, the metal part 60 that surrounds the core 20 is removed from the mold 50. wherein the core 20 forms a hollow space inside this part. In order to separate the core 20 from the part 60, it is subjected to a conventional core removal process, typically mechanical and / or hydraulic. The core 22 of the core is crushed by the combined effect of thermal decomposition of the binders that form the base (this decomposition occurs during injection of the liquid metal under the influence of the temperature of the above metal) and the core removal efforts. If the composition allows, the frame 36 can also be destroyed simultaneously with the base 22. Otherwise, the frame 36 can be removed after removing the base 22. for example, by acting on the part using a second core removal process. In this example, the elements resulting from the grinding of the base 22 and the frame 36, if provided, are removed through the end holes 62 of the hollow tubular part 60. The support elements 18 are removed simultaneously with the base 22 through the above holes 62. It should be noted that these holes 62 pass through the part 60 and the sheath 40. In another example, which is not shown, outlet openings are provided by removing the support elements 18 from the core 20.

In this way, the hollow metal part 60 shown in FIG. 5, while the inner side of the above part 60 is covered by a shell 40. Then, the shell 40 is destroyed and removed through the holes 62 to obtain a separate part 60. For example, the shell 40 is destroyed by bead-blasting or core removal using water under pressure (5-50 MPa ) depending on the strength of the part 60.

For example, it is possible to manufacture part 60 by conventional die-casting of an aluminum-silicon-copper alloy. The discharge pressure can be 100-1200 bar (i.e. 10-120 MPa), and the metal feed rate can be 10-80 m / s. The silicon content may be 2-20%, and the copper content may be 0.1-10%. For example, AlSi9Cu3 (Fe) alloy can be used.

In the present description, embodiments or examples of implementation are given by way of explanation and are not restrictive, and those skilled in the art, in light of the present description, can easily modify these embodiments or examples or provide other modifications or examples that are within the scope of the present invention.

In addition, various features of these embodiments or implementation examples may be used in parallel or in conjunction. In the case of sharing, these features can be combined as described above or in another way, and the invention is not limited to the specific combinations described in the present invention. In particular, unless otherwise indicated, the distinguishing feature described in relation to an embodiment or implementation example may similarly be used in another embodiment or implementation example.

Claims (19)

1. A method of manufacturing a hollow metal part by casting, in which: provide a destructible core (20), which includes a base (22) made of filler, and a shell (40) surrounding the above base and attached to it, and a frame (36) passing through the core base (22) and connected to sheath (40), the core (20) is placed inside the mold (50); the metal is melted and the liquid metal is injected into a mold (50) surrounding the core (20), which forms the space inside the part (60); after curing of the part (60), the base (22) is ground and removed through the holes (62) for removal provided in the shell (40) and in the part (60); destroy the above shell (40) and remove it through the holes (62) for removal provided in the part (60); destroy the frame (36) and remove simultaneously with the base and / or shell; in this case, for the manufacture of the core (20), the core (22) of the core is made by aggregating materials in a molding box (10) equipped with pins (16) passing through the inner side of the molding box so that, after being removed from the molding box, the base has holes (26) in place of the pins, and the holes (26) are filled with the material forming the frame (36). 2. The method according to p. 1, in which the liquid metal is injected under pressure into the mold (50) surrounding the core (20), while the shell (40) has sufficient mechanical strength to withstand the injection under pressure of the liquid metal. 3. The method according to p. 1, in which the holes (26) and the corresponding frame element pass through the entire base (22) of the core (20). 4. The method according to p. 1 or 3, in which the core (22) of the core is immersed in the first liquid clay solution to form the frame (36) and the lower layer of the shell (40), and then in one or more liquid clay solutions to form one and several upper layers of the shell (40). 5. The method according to claim 1, in which, for the manufacture of the core, the core (22) of the core (20) is made by aggregating materials in a molding box (10) provided with support elements (18) passing through the inside of the molding box, and the shell (40), the surrounding base (22), and the supporting elements (18) are made so that the supporting elements pass through the shell, while the supporting elements (18) are used to hold the core (20) in place in the mold (50) during injection. 6. The method according to p. 5, in which the supporting elements (18) are hollow and form the outlet channels for gases, which are formed during thermal decomposition of certain components of the core (20) during casting. 7. The method according to p. 5 or 6, in which, after curing the part (60), the support elements (18) are removed from the part to obtain removal holes through which the core (22) of the core and / or the shell (40) are removed. 8. The method according to claim 1, in which the core (22) of the core is made of foundry sand or molding gypsum, possibly with a fibrous filler. 9. The method according to claim 1, in which the shell (40) of the core is made of ceramic. 10. The method according to claim 1, in which the base (22) is ground and removed mechanically and / or hydraulically.

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